This invention relates to motor vehicle power plants, and more particularly, to xe2x80x9chybridxe2x80x9d motor vehicles powered by both electrical and fossil fuel power plants. Still more particularly, the present invention relates to a parallel hybrid electric/fossil fuel power plant for a motor vehicle such as a passenger car, in which the electric motor shaft is connected in parallel with an internal combustion engine shaft, and the electric motor is controlled to balance the load of the internal combustion engine.
For most of the 20th century, the gasoline or diesel powered internal combustion engine has been extremely successful in powering motor vehicles throughout the world. The internal combustion engine efficiently delivers high power outputs by converting fossil fuels such as gasoline into mechanical power. Despite its many advantages, however, the fossil-fuel powered internal combustion engine has some significant drawbacks:
it requires fossil fuels, an expensive, limited resource; and
it pollutes the air with poisonous and environmentally damaging combustion byproducts.
These drawbacks are so significant that there has recently been a massive worldwide effort to come up with alternatives.
The all-electric vehicle is one possible alternative. In this all-electric alternative, an electric motor and a source of electric power would replace the internal combustion engine. The electric motor would provide power to drive the wheels, and the electric power source would deliver electricity to drive the motor. An all-electric vehicle has zero exhaust gas emissions and requires no fossil fuels. Widespread use of all-electric vehicles would decrease the economic dependency of major industrialized nations on foreign oil producing countries, and could help us provide cleaner air.
Millions of dollars have been poured into research and development of a practical, commercial all-electric vehicle design that can realize these objectives. Unfortunately, the first practical cost-effective mass-produced all-electric vehicle is still many years away. For the same reasons that the first experimental electric vehicle designs were thrown aside in the last century, all-electric vehicles simply cannot compete with fossil fuel powered vehicles. The problem has to do with efficient power storage.
Because a motor vehicle moves, it must be self-contained and store its own power. Ideally, the power storage should be small, lightweight, and deliver a lot of power. Today""s motor vehicles carry two different power storage devices: an electric battery and a gasoline tank. Most of the vehicle""s power comes from the gas tankxe2x80x94with the electric battery contributing only enough power to turn a starter motor that gets the internal combustion engine started. Why?
By weight, gasoline stores on the order of fifty times the power versus a battery of the same weight. You would need about a ton of electric batteries to store the same amount of power provided by the gasoline held by the average passenger car fuel tank. Such a large quantity of electric batteries would cost on the order of several thousand dollars, would be very bulky, and may need to be replaced every few years as they wear out.
The batteries also have to be recharged somehow once they become xe2x80x9cdead.xe2x80x9d In today""s cars, an alternator converts power from the internal combustion engine into electricity for recharging the battery. If there were no internal combustion engine, the recharging power would have to come from some other source. While some recharging power could come from the force of gravity (for example, the momentum from going down a hill could be converted into electricity), most of the recharging power would have to come from somewhere elsexe2x80x94such as an electric wall socket the car owner plugs his car into every night.
This battery recharging process could take many hours or even overnightxe2x80x94as compared with the essentially instant refilling of a passenger car gas tank at a filling station. This means that an all-electric vehicle inherently has a very limited range. The driver would have to stop for the night whenever the batteries discharged too much.
Although many people don""t realize it, battery recharging from a wall socket can also cause pollution. The idea that electric power is clean and non-polluting is a fiction. Although some electric power plants (for example, nuclear and hydroelectric power plants) do not pollute the air, the vast majority of electric power plants in the United States burn coal or other combustible materialsxe2x80x94and therefore are major polluters. Some people say that an all-electric vehicle would simply move air pollution from individual car exhausts to electric power plant smokestacks.
Major research has been devoted to improving the storage capabilities of electric batteries. Modern batteries are lighter, longer lasting and more powerful than their predecessors from years past. However, the fact remains that filling a gasoline tank is a much more convenient and less expensive way to store power for a high speed, long distance motor vehicle. Human nature being what it is, people are generally reluctant to personally sacrifice a lot of time and money to help the environment. Recycling newspapers is one thing, but spending $15,000 for a car that cannot go on long trips is another thing entirely.
Because battery powered all-electric vehicles cannot compete with vehicles having internal combustion engines, some people have tried to develop so called xe2x80x9chybridxe2x80x9d electric vehicles that use both electric and gasoline power. The basic idea is that a hybrid electric vehicle may provide many of the advantages of both electric and fossil fuel power storage while eliminating at least some of the drawbacks of each. The U.S. Department of Energy has become committed to making hybrid electric vehicles commonplace on American highways by the year 2003. Its National Renewable Energy Laboratory (NREL) is working with industry to develop hybrid vehicles with high fuel economy and low exhaust emissions. The NREL is supporting development programs at General Motors, Ford Motor Company, Chrysler Co., and a variety of independents. Other major automotive manufacturers throughout the world are working on the same problem.
All of this work by all of these different people has led to a number of different hybrid electric approaches. One common approach is the so-called xe2x80x9cseriesxe2x80x9d design. The xe2x80x9cseriesxe2x80x9d design attempts to solve some of the battery problems discussed above by using an internal combustion engine to generate electrical power. In the xe2x80x9cseriesxe2x80x9d design, a fossil-fuel powered internal combustion engine turns the shaft of an electric power generator. The generator""s electrical output powers the electric motor. The electric motor is used to turn the vehicle""s wheels.
This xe2x80x9cseriesxe2x80x9d hybrid design has the advantage of reducing the number and weight of the electric batteries required to power the vehicle. Because the vehicle generates electrical power as it goes, it does not need as many electric batteries and also avoids a long battery recharge time. In addition, the gasoline engine can be operated under essentially constant conditions that can provide low exhaust emissions and low fuel consumption. But this xe2x80x9cseriesxe2x80x9d hybrid electric vehicle has some significant drawbacks. Its main drawback is that it is very inefficient in its use of gasoline. The process of converting the mechanical power produced by the gasoline engine into electrical power using a generator for powering the electric traction motor is relatively inefficient. This inefficient process wastes power.
A different approach is the so-called xe2x80x9cparallelxe2x80x9d hybrid-electric design. In the xe2x80x9cparallelxe2x80x9d approach, an internal combustion engine and an electric motor can both apply power to a motor vehicle drive train. See, for example, Kalberlah, xe2x80x9cElectric Hybrid Drive Systems For Passenger Cars and Taxisxe2x80x9d, SAE Publication No. 910247 for a survey of various parallel hybrid electric designs. There are many such xe2x80x9cparallelxe2x80x9d hybrid designs:
Some such prior xe2x80x9cparallelxe2x80x9d designs never operate the electric motor and the internal combustion engine in parallel at the same time. Instead, the electric motor is used for city driving and other short trips, while the internal combustion engine is used for longer trips requiring greater range.
Other parallel hybrid designs use complicated clutches or differentials to couple the engine and the motor to the drive train. Such mechanical linkages are heavy, expensive and can be unreliable.
Still other parallel hybrid designs drive one pair of wheels with the electric motor and the other pair of wheels with the internal combustion engine. This approach can cause steering and safety problems.
While prior parallel hybrid approaches have met with limited success in the laboratory or on the test track, no practical mass-produced commercially available passenger vehicle has yet been produced using this technology. Further improvements are desperately needed.
The present invention provides a new parallel hybrid electric vehicle design that delivers smooth, high power performance while decreasing harmful exhaust emissions and maximizing fuel economy.
In accordance with an aspect of the present invention, a battery-powered electric motor assists the internal combustion engine. During typical vehicle operation, most of the vehicle""s power comes from the internal combustion engine. The electric motor is controlled to output power under certain operating conditions to assist the internal combustion engine. In particular, the electric motor provides a xe2x80x9cload levelingxe2x80x9d function that improves performance and driveability while maximizing fuel economy and reducing harmful emissions.
In one non-limiting example, a controller can control the electric motor to assist the internal combustion engine during times when the engine is called upon to produce a rapid speed RPM change (for example, upon acceleration from low to high speed). It is during such rapidly changing conditions that the internal combustion engine runs least efficiently and produces a lot of harmful exhaust emissions. By controlling the electric motor to xe2x80x9cload balancexe2x80x9d the internal combustion engine during these rapidly changing conditions, it is possible for the controller to control the internal combustion engine to operate in ways that might otherwise be unacceptable from a performance or other standpoint.
For example, the controller can supply the internal combustion engine with less fuel so it runs xe2x80x9cleanerxe2x80x9d during times when the electric motor is assisting the engine-increasing fuel economy and dramatically reducing harmful exhaust emissions. Even though the internal combustion engine operates very xe2x80x9cleanxe2x80x9d, overall vehicle performance doesn""t suffer (and can actually be improved) because the electric motor provides power assist to make up for decreased internal combustion engine torque output. The resulting power train operation is exceptionally smooth and powerful. The acceleration curve is rapid and continuous. Depending on the particular system characteristics and system design and operating criteria, acceleration performance can be improved dramatically relative to a non-hybrid system while improving fuel economy and lowering harmful exhaust gas emissions.
In one particular example, the controller may operate the electric motor as an electrical generator during times when the internal combustion engine produces (or the vehicle drive train otherwise has) more power than the vehicle needs. For example, during vehicle deceleration or regenerative braking and vehicle idle, the internal combustion engine produces excess power that can be used to recharge the batteries powering the electric motor. During such excess power conditions, the controller controls the electric motor to act as a generator to convert excess mechanical energy from the internal combustion engine to electrical energy. This electrical energy is used to recharge the electric battery.
The following is a non-exhaustive summary of further non-limiting features and advantages provided by the invention:
Low emissions.
Smooth, high performance operation.
Simple, seamless, reliable design.
Relatively low cost.
Electrical assist mechanical balancing.
Electric motor provides xe2x80x9cload levelingxe2x80x9d to satisfy peak and/or changing power demands due to acceleration and other rapidly changing conditions.
Electric motor produces torque to overcome the need for the internal combustion engine to satisfy rapidly changing power demandsxe2x80x94resulting in better fossil fuel economy and lower exhaust gas emissions
Electrical assist may be sized to load level the internal combustion engine.
Battery power provides enhanced lean running for higher energy efficiency even at idle.
Internal combustion engine is directly connected to the electrical motor, and both are connected to the vehicle drive train.
A seamless connection is made between the electric motor and internal combustion engine using grooved belts and gears.
No clutches are required.
No need for an energy storage flywheel.
Smooth torque control that varies from full power to zero power using an electrical assist computer.
Real time electrical assist computer operation can continually adjust motor and engine control parameters in response to sensed vehicle operating conditionsxe2x80x94providing a fast response closed loop feedback control system.
Performance enhancement can be realized when both power sources are used.
Major charging can occur at the xe2x80x9csweetxe2x80x9d spots of the engine where maximum internal combustion engine efficiency occurs. (The electrical battery power supply is charged on an ongoing basis, the internal combustion engine running in its xe2x80x9csweet spotxe2x80x9d and the electric motor running as a generator to recharge the battery).
Utilize an electrical assist computer to monitor the functions of an internal combustion engine and, based on this information, the electrical assist computer gives appropriate commands to the electric motor.
Electrical assist computer can operate the electric motor in any of three different drive modes: drive, charge and neutral.
Modified Electronic Engine Management System can be used to monitor battery charge state and electric motor current and voltage, and to control the current delivered by the electric motor to charge the battery and used by the electric motor when assisting the engine.
The electrical motor is used for charging or producing power.
Battery charging at idle eliminates the problem of power waste at idle.
When the battery is fully or near fully charged, the electrical assist is used to reduce fuel consumption.
No relays or mechanical off-on switches are required for control except main power on-off using keys.
Electronically stored tables can be used to define the amount of current the motor uses to assist or charge, all over the engine operating range (Load vs. RPM). The amount can be derived empirically.
The Electrical Assist Computer modifies the charge current from zero to maximum as a function of the currently sensed state of charge.
Another possible mode is to have wall socket charging to obtain maximum power assist and fuel economy.
Not necessary to plug into wall socket to charge but this can be done for very high fuel economy.
Uses a battery with or without industrial capacitors. With capacitors in parallel the battery is balancedxe2x80x94reducing high demand or charge currents from damaging the battery and expanding the energy storage capacity.
Battery/motor weight and size can be selected to be about the weight and size of parts taken off the engine because they are not used, providing a negligible increase in overall vehicle weight (e.g., no more than a few pounds weight gainxe2x80x9475 lbs. on a 3,000 lb. car) after redundant parts are removed.
Using gasoline stored in tank extends the range of the vehicle many times over what could be obtained on electric power alone.
The electric motor can replace an alternator, generator, and, at the same time, is a traction motor.
The electric motor""s output shaft can be directly coupled to the internal combustion engine""s crankshaft.
A real-time computer-based electronic controller can be used to optimally control both the internal combustion engine and the electric motor.
The controller can monitor vehicle operating parameters in real time, and optimizes the electric motor""s operation (and, if desired, also the operation of the internal combustion engine) to achieve desired operation characteristics including, but not limited to, maximal efficiency, best fuel economy, desired vehicle range, highest performance and/or lowest exhaust emissions.
The controller can provide very rapid real time responsexe2x80x94making possible closed loop real time feedback control of the overall parallel hybrid motor/engine system.
The electric motor controller can phase the internal combustion engine and electric motor together so that pulse width pockets of power are applied at specific angled engine events even with a rapid speed and load changexe2x80x94providing a net effect of a smoother, cleaner and more efficient internal combustion engine.
The controller can operate the electric motor in neutral or xe2x80x9cinvisiblexe2x80x9d mode. This neutral mode can be used to prevent battery overcharging during times when electric motor power assist is not needed and/or to avoid further loading the internal combustion engine during less efficient engine operations.